<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h1>0</h1>
<h2>0</h2>
<script>
  setInterval(f,1000);
  let count = 0 ;
  function f() {
    count++;
    let h = document.querySelector("h1");
    h.innerText = count;
  }
  let x = 0;
  let timer = setInterval(function () {
    x++;
    let h = document.querySelector("h2");
    h.innerText = x;
    if (x>50){
      clearInterval(timer);
    }
  },100);

  setTimeout(function () {
            x=50;
          },3000);
</script>
</body>
</html>